1. Field of the Invention
The present invention relates to a light-emitting device including a plurality of light-emitting elements and a method of manufacturing the light-emitting device.
2. Description of the Related Art
In recent year, in the field of semiconductor lasers, multiwavelength lasers including a plurality of light-emitting sections with different emission wavelengths on a common substrate (or a common base) have been actively developed. The multiwavelength laser is used as, for example, a light source for an optical disk device.
In such an optical disk device, 700-nm-band laser light is used to replay a CD (a Compact Disk), and to record and reproduce data to/from a recordable optical disk such as a CD-R (a CD Recordable), a CD-RW (a CD Rewritable) or an MD (a Mini Disk). Moreover, 600-nm-band laser light is used to record and reproduce data to/from a DVD (a Digital Versatile Disk). When the multiwavelength laser is mounted in the optical disk device, the optical disk device is allowed to record and reproduce data to/from a plurality of kinds of already available optical disks. Moreover, a short-wavelength (400-nm band) laser using a nitride-based Group III-V compound semiconductor (hereinafter referred to as “GaN-based compound semiconductor”) typified by GaN, AlGaN and GaInN has been achieved, and the short-wavelength laser has been developed for practical use as a light source for a higher-density optical disk. When lasers including the short-wavelength laser have more wavelengths, the application of the lasers is expanded.
As a three-wavelength laser element (light-emitting device) including such a GaN-based laser oscillator, for example, a three-wavelength laser element manufactured by the following method has been proposed in related art, for example in Japanese Unexamined Patent Application Publication No. 2007-48810. That is, first, a first light-emitting element with a 400-nm-band wavelength is formed by growing a GaN-based compound semiconductor on a substrate. Moreover, a 600-nm-band element formed by growing an AlGaInP-based compound semiconductor and a 700-nm-band element formed by growing an AlGaAs-based compound semiconductor are arranged in parallel on the GaAs substrate to form a second light-emitting element. Then, the first light-emitting element and the second light-emitting element are laminated in this order on a supporting base. The three-wavelength laser element is formed in such a manner in related art. In the three-wavelength laser element in related art, heat generated in the second light-emitting element is dissipated from the GaN substrate or the supporting base both of which have good thermal conductivity, so high heat dissipation efficiency is obtained.
There are disclosed two modes of the light-emitting device, that is, a first light-emitting device and a second light-emitting device. In the first light-emitting device, a first light-emitting element is mounted on a supporting base, and a plurality of columnar posts are formed on the supporting base, and then a second light-emitting element is mounted on the columnar posts and the first light-emitting element. The columnar posts have a function as a heat sink dissipating heat generated in the second light-emitting element, and a function of supplying electric power to the second light-emitting element from the supporting base side. The columnar posts are obtained by arranging tungsten or copper in predetermined positions on the supporting base by a printing method, and then firing tungsten or copper.
On the other hand, in the second light-emitting device, a depression section is formed in a supporting base, and a first light-emitting element is contained in the depression section, and a second light-emitting element is arranged on the supporting base and the first light-emitting element.